1. Field of the Invention
This invention relates to lubricating oils, and more particularly to improved lubricating oils containing hydrocarbon derivatives of 2,5-di-mercapto-1,3,4-thiodiazole as copper corrosion inhibitors, terephthalic acid as a lead corrosion inhibitor, sulfur bridged, bis hindered phenols as an oxidation inhibitor, and certain boron and/or metal-boron derivatives having extreme pressure, anti-wear and friction reducing properties.
2. Description of the Prior Art
The use of boron containing compounds as extreme pressure and anti-wear additives for lubricating oils is known and appreciated by the prior art. For example U.S. Pat. No. 3,313,727 to Peeler discloses compositions of amorphous alkali metal borates as a stable dispersion in lubrication oils. In particular, a boron compound, such as, the metaborates and tetraborates of sodium and potassium in combination with a lyophilic surface active agent, such as the carboxylates, phenates and sulfonates of alkaline earth metals, e.g. calcium and barium, when dispersed in lubricating oil compositions are said to improve the extreme pressure and anti-wear properties thereof.
U.S. Pat. No. 2,987,476 to Hartley et al. relates to a method for solubilizing boric acid and metal borates in liquid fuels for internal combustion engines and in lubricating oils and greases. Desirable compositions are prepared by hydrolyzing an organic ester of boric acid in the presence of three materials, namely, a lyophilic ionic surface active agent, a non-polar organic liquid and a water-miscible organic liquid. The resulting dispersible boron-containing product of this process is a complex of an inorganic boric acid compound with an oleophilic ionic surface active agent.
Another boron composition is disclosed in U.S. Pat. No. 3,598,855 to Cyba which relates to cyclic borates of polymeric alkanolamines formed by reacting a borylating agent with a polymeric alkanolamine. The additives thus formed are described as additives for a wide variety of petroleum products including lubricating oils.
U.S. Pat. No. 3,227,739 to Versteeg relates to lubricating oils containing additives formed by reacting certain amine type compounds with boric acid. The amine type compounds are prepared by reacting equal molar proportions of diethanolamine or dipropanolamine and a long chain 1,2-epoxide.
Another extreme pressure lubrication composition is disclosed in U.S. Pat. No. 3,185,644 to Knowles et al., which relates to lubricating compositions containing amine salts of boron-containing compounds. The amine salts are formed by reaction of a hydroxy substituted amine and a trihydrocarbyl borate. The amine-borate compounds thus formed are described as useful as load carrying additives for mineral and synthetic base lubricating oils.
As can readily be determined from the above, there is an ongoing effort to develop improved lubricating compositions which contain boron and/or boron derivatives.
Accordingly, it is an object of the present invention to provide an improved lubricating composition having enhanced extreme pressure, anti-wear and friction reducing properties.
Another object of the present invention is to provide a lubricating composition having improved copper and lead corrosion properties.
Yet another object of the present invention is to provide a lubricating composition having improved antioxidant properties.
A further object of the present invention is to provide a lubricating composition containing extreme pressure, anti-wear, friction reducing and corrosion prevention additives, plus an anti-oxidant to prevent attack of oxidants upon copper/lead-bearing metal.
These and other objects are accomplished according to the present invention by adding to a lubricating composition a small but effective amount of a boron and/or metal boron additive in combination with copper and lead corrosion prevention additives and anti-oxidant.